1. Field of the Invention
The present invention relates to a magnetron sputtering apparatus for producing thin films on substrates, which enables one to maintain the sputtering conditions constant during the sputtering operation, thus making it possible to produce uniform thin films of good quality.
2. Description of the Prior Art
There are many sputtering apparatus of various systems such as, for example, diode DC sputtering systems, triode DC sputtering systems and radio-frequency sputtering systems which are used for producing thin films on substrates. In such sputtering apparatus a magnet is fixed on the opposite side of an electrode which is adapted to hold a target, to accelerate ionized atoms of, an ionizable medium such as argon, oxygen and the like which sputter film-forming atoms from the surface of the target, thus making it possible to use high electrical power or to increase the sputtering rate.
However, the thickness of the target decreases with the progress of sputtering since the film-forming atoms are ejected from the surface of the target. This results in a change in the distance between the magnet and the surface of the target because of the fixed distance between the magnet and the electrode which are positioned opposite each other. Since the distance between the magnet and the surface of the target affects the magnetic flux density at the surface of the target, it is difficult to produce uniform thin films, even if other conditions such as the voltage applied to the cathode and the atmosphere are maintained constant.
It is therefore an object of the present invention to provide a sputtering apparatus for producing uniform thin films.
According to the present invention, there is provided a sputtering apparatus comprising at least two spaced apart electrodes which are positioned opposite to each other, one of said electrodes having a space provided therein and being used for mounting a target thereon, from which film-forming atoms are ejected by ion-bombardment, and the other electrode being used for mounting a substrate thereon. A magnet is disposed in said space by being mounted on means adjusting for adjusting the distance between the target and the magnet, said means for adjusting said distance being provided in said one electrode.
In a preferred embodiment of the present invention, means for adjusting the distance between the magnet and the target comprises a support movably arranged in said one electrode on which the target is mounted, and an adjustment screw loosely or fixedly secured to the support at its screw end and engaged with a tapped bore provided in the bottom of said one electrode.
In another embodiment of the present invention, means for adjusting the distance between the magnet and the target comprises a disk-shaped support provided with an external thread which is adapted to engage in an internal thread provided in the cylindrical electrode, and an adjustment shaft fixed to the disk-shaped support.
The magnet may comprise one or several permanent magnets or electromagnets.
According to the sputtering apparatus of the present invention, the magnetic flux density at the surface of the target can be adjusted by adjustment of the distance between the target and the magnet, thus making it possible to produce thin films with uniform characteristics even if the sputtering is repeated many times without exchange of the target. Furthermore, by keeping the initial magnetic flux density constant it is possible to improve the adhesion between the thin film and the substrate. In addition, it is possible to produce piezoelectric crystalline films of good orientation.